Electric furnace

My electric furnace had a fuse that had been wrongly replaced to a 60 amp fuse which made one of the wires start to eat at the insulation. i replaced the 60 amp fuse to a 50amp fuse (correct fuse) and then a week later the fuse went out again and now my furnace does not work. Any ideas? I was thinking of replacing all of the wires since it has not been done in a while.